Air-compressor



(No Model.)

W. A. PITT.

AIR GOMPRESSOB..

No. 386,028. `Panmafnted July 10, 1888.4

UNITED STATES PATENT OFFICE.

VILLIAM A. PITT, CF GLENBROOK, CONNECTICUT.

AlR-ooMPREssoR.

w; SPECIFICATION forming part of Letters Patent No. 386,028, dated Julyl0, 1888.

Application filed June 30, 1837.

Serial No. 243,048. (No model.)

To all whom it may concern.-

Be it known that [,WILLTAM A. PITT, a citizen ofthe UnitedStates,residing atGlenbrook, in the county of Fairfield and State ofConnecticut, have invented certain new and useful Improvements inAir-Compressors, of which the following is a full, clear, and exactspeciiication.

The purpose of my improvement is to provide means whereby an equivalentin compressed air in volume or pressure is obtained for the powerexpended in compression. This I accomplish by acertain mechanicalarrangement which is substituted for the crank, connecting-rod, andiiy-wheel heretofore employed for the transmission of power from thepiston of a steamengine,and through which the piston-rod is caused toact at the full or `weaker end of the stroke with as much power as wasexpended in propellingit at the beginning of its stroke. l

In the accompanying drawings, which clearly illustrate my improvedmechanism, Figure l is a side elevation of an air-compressor con tainingthese improvements, a portion of the bed orl'rame being broken away toshow the operating parts. Fig. 2 is a top plan view of the same; andFig. 3 is an end view thereof, the lower portion being broken off.

Let a represent the bed or frame of the machine supportingthe operatingmechanism,and

b, the steam-cylinder, and c the air-cylinder,

both being of equal dimensions.` dand e are respectively the piston-rodsof the steam and airA cylinders. On the outer end ofthe piston-rod d isformed a rack, d, and a similar rack, e', is provided on the airpiston-rod e. The teeth of both racks are made to mesh into or engagewith a centrally-mounted gear or spur wheel, f.

g and h are longitudinal blocks or strips secured, respectively, to thetop and bottom portions of the frame a by means of bolts z', to formbeds or guideways within which the rack ends of the two pistons slideand by which they are kept in constant engagement with the spurwheel f.These guides may be cast on the frameA a, if desired, instead of beingbolted thereto.

j is the shaft on which the spur-wheel fis mounted. The ends of thisshaft are projected through a vertical slot or opening, Ic, formed ineach side of the frame a, so that on the rotation of the spur-wheel itsaxis is caused to v travel in a vertical line to and fro within theopening 7c, and becomes, as it were, a changeable fulcrum from thebeginning to the finish ofthe stroke of the piston-rod d.

Z represents a spray-nozzle connected with any suitable apparatus, whichis so arranged as to inject a spray of water into the rear end oftheairleylinder c, which is left open in order to keep the piston andvalves cool `either while the piston-rod is or is not in motion.

The operation of the device is as follows: Steam being admitted into thecylinder b gives to the rack d a forward Amovement to the left, whichrotates the gear-wheel fand imparts to the rack e a reverse or forwardmovement to the right. Asthegear-wheelbeginstorevolve its axisj is moveddownwardin its slot to midway between the two racks, the engine in itsmovement making a short thrust of the pistonrod d and causing a longthrust of the air piston-rod e, as is clearlyindicated by dotted linesin Fig. l, whereby the gradually-increasing resistance is overcome tothe point indicated. From that point the movement is'reversed. The longthrust of the steam-piston causes a short thrust of the air-piston e,which overcomes the greater and constantly-increasing resistance.

In applying my method to air-compression it is usual to place the axisor movable shaft at a distance of about one-fourth of the radius fromthe periphery of the gearfwhe'el,whereby, with one-quarter of the strokeof the steampiston, I am enabled to cause athree-quarters stroke of theair-piston, at which point the axis is equidist'ant from the racks andthe 1everage equal and the gear-wheel f one-fourth revolution totheright, which results, at the point indicated, in having'securedangequivalent of compressed air both in volume and pressure for theamount of steam expended. Now, from this point,as theaxisj movesdownward in the slot lc toward the point marked 2, wehave, to commence,three-fourths stroke of the steam-piston left to make one-quarter strokeof the air-piston, -either to deliver the air in volume and pressureasalready attained,4 the steam being cut off after the one-quarter travelof its piston to complete such result, or to allow the steam to be cutoff later on in its travel and permit an equivalent in volume of thecompressed air to be delivered, only at a much higher pressure, as maybe desirable, and proportionate to the point Whereat the steam shallhave been cnt off inthe steamcylinder.

My improved device is equally applicable to all engines, in which casesI am enabled to utilize the full expansive property ofthe steam withoutdiminished result.

Referring to the drawingait will bc observed that the air-cylinder c isleft open on one end, so that the air is only compressed at one end ofthe cylinder, the object being` to afford as much time as possible for aradiating away of the heat absorbed while effecting the compression.

By my device it will be seen that While the greater Compression istaking place, and from the commencement of the working-stroke of theair-piston, the speed is diminished proportionately, thereby effectingthe truc requirement necessary for the cooling process inaircompression.

lVhat I claim as new, and desire to secure by Letters Patent, is

l. The combination, in an air-compressor,

of a steam-cylinder and air-cylinder with their piston-rods, eachprovided with a rack end, and a gear-wheel having a movable axisarranged to engage with said racks, substantially as set forth.

2. Thecombinatio11,\vit11ihesteanrcylinder, aircylinder, and theirpiston-rods, each having a rack end, of aspur-Wheel mount-cd on an aXislocated near the periphery of the wheel and arranged, substantially asdescribed, to have a vertical movement in the frame ofthe engine duringthe revolution of the Wheel, whereby it becomes a changeable fulcrumfrom the beginning to thcnish ofthe stroke ofthe steampiston, as setforth.

3. In combination, the steam cylinder b, aircylinder c, having an openend, nozzle l, pistonrods d e, with racks d and e', toothed wheel f,shaftj, and frame a, with slot k, as set forth.

4. The combination of the frame a, having guideways f/ and lf,piston-rods (l and c, racks d/ and e', spur-wheelf, adapted to engagesaid racks, and shaftj, arranged to move in a Vertical slot in the framea, as Set forth.

V I TiLl AM A. PITT.

,Vitnesses:

S. J. JONES, K. NEWELL.

